Sealing adapter for well tubing head

ABSTRACT

A tubing head adapter which operates to provide a supplemental sealing barrier for a tubing head while maintaining access to the interior of the tubing head. The adapter includes an annular body adapted to be secured in fixed relation to the tubing head and a dummy hanger adapted to be matedly inserted into the annular body. The dummy hanger includes an annular sleeve insert and a removable axial plug disposed within the annular sleeve insert. A plurality of extendable and retractable locking pins secure the dummy hanger in place.

TECHNICAL FIELD

The present invention relates generally to barrier systems for wells, and more particularly, to a barrier system adapted to provide secondary protective sealing for a tubing head operatively engaging an oil or gas well.

BACKGROUND OF THE INVENTION

It is well known to increase production from oil and gas formations by so called “fracturing” to increase the permeability of the production zone. In general, fracturing involves pumping pressurized fluids through perforations in a well casing into a production zone in order to break or fracture pores in the production zone. In the fracturing procedure, fracturing fluids are pumped under very high pressures of about 5,000 to 10,000 psi through the perforations into the formation. The high pressure breaks the formation to form flow channels for hydrocarbon fluids. In practice, it is common to carry out fracturing procedures for a collective group of wells and to then seal some or all of those wells for a period of time until production operations commence.

Oil and gas wells are typically provided with a production tubing head (also known as a tubing spool) which serves as a connection for the fracturing equipment as well as for the introduction tubing or other equipment into the well interior during production. As will be appreciated, following the fracturing operation, the well typically has a substantial positive pressure as hydrocarbons seek to exit from the production zone. Once the fracturing equipment is removed, it is therefore necessary to seal off the tubing head to avoid backflow from the well and to avoid the introduction of debris into the tubing head. As part of this sealing procedure, it is common to introduce a tubing hanger into the axial bore of the tubing head to provide an axial seal.

The use of such tubing hangers is considered generally desirable due to the ease of use and ability to maintain full bore access by removing the hanger. However, it has been found that tubing hangers may be susceptible to damage and/or may permit a pressure leak when subjected to high pressure over extended periods following the fracturing operation. Accordingly, a supplemental tubing head barrier that may be adapted to function with existing tubing head constructions to provide additional sealing protection without unduly limiting access to the tubing head interior would be desirable.

SUMMARY OF THE INVENTION

The present invention provides advantages and alternatives over the prior art by providing a tubing head adapter which operates to provide a supplemental sealing barrier for a tubing head while maintaining access to the interior of the tubing head. The present invention also provides a dual barrier stack-up completion that allows removal of the fracture stack and production tree installation with dual barriers between produced hydrocarbons and the atmosphere.

In accordance with one aspect, the present invention provides an adapter for disposition in sealing relation to a tubing head operatively connected to a hydrocarbon well. The adapter includes an annular body adapted to be secured in fixed relation to the tubing head. The annular body includes an axial channel, a first set of radial locking pin channels extending radially away from the axial channel and at least a second set of radial locking pin channels extending radially away from the axial channel. The second set of radial locking pin channels are axially spaced from the first set of radial locking pin channels. The adapter further includes a dummy hanger adapted to be matedly inserted into the axial channel. The dummy hanger includes an annular sleeve insert having a central bore and a removable axial plug disposed within the central bore. The annular sleeve insert includes a plurality of pin receiving channels extending radially through the annular sleeve insert for aligned relation with the first set of radial locking pin channels. A first set of extendable and retractable locking pins are disposed within the first set of radial locking pin channels. The first set of extendable and retractable locking pins includes distal ends adapted to project through the pin receiving channels in the annular sleeve insert to engage the axial plug. A second set of extendable and retractable locking pins are disposed within the second set of radial locking pin channels. The second set of extendable and retractable locking pins include distal ends adapted to engage the annular sleeve insert. A first compressible seal is disposed circumferentially about the annular sleeve insert. At least a second compressible seal is disposed circumferentially about the annular sleeve insert in axially spaced relation from the first compressible seal. At least a third compressible seal is disposed circumferentially about the axial plug. At least a fourth compressible seal is disposed circumferentially about the axial plug in axially spaced relation from the third compressible seal.

Other exemplary constructions, features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side sectional view of an exemplary tubing head with a tubing hanger in place and with an exemplary sealing adaptor consistent with the present disclosure in place across the tubing head with a dummy hanger sleeve and axial plug removed;

FIG. 2 is a side sectional view of the exemplary sealing adapter of FIG. 1 showing the dummy hanger annular sleeve insert and axial plug in place; and

FIG. 3 is a sectional plan view taken generally through line 3-3 in FIG. 1 showing an exemplary positional arrangement for locator pins and locking pins holding the dummy hanger annular sleeve insert and axial plug in place;

FIG. 4 is a side sectional view of an alternative embodiment of the invention providing a unibody tubing head and sealing adaptor with a tubing hanger in place in the tubing head portion with a dummy hanger sleeve and axial plug removed.

Before the embodiments of the invention are explained in detail, it is to be understood that the invention is in no way limited in its application to the details of construction and/or to the arrangements of the components set forth in the following description or illustrated in the drawings. Rather, the invention is capable of other embodiments and of being practiced or carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein are for purposes of description only and should not be regarded as limiting. The use herein of “including”, “comprising”, and variations thereof is meant to encompass the items listed thereafter and equivalents, as well as additional items and equivalents thereof.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made to the drawings. To the extent possible, like elements are designated by like reference numerals in the various views. Referring to FIG. 1, a production tubing head 12 (also referred to as a tubing spool) is shown with a tubing hanger 14 in place within the axial bore 16 of the tubing head 12. In practice, the tubing head 12 is operatively connected to a well casing (not shown) in a manner as will be well known to those of skill in the art. As shown, the tubing head 12 may include a connection leg 18 for attachment of fracturing equipment or the like. In the illustrated exemplary arrangement, the connection leg 18 may be sealed by use of an isolation valve 20 and a flange seal 22. Thus, the tubing hanger 14 in combination with the isolation valve 20 and the flange seal 22 act to provide primary sealing of the production tubing head 12. However, other primary sealing arrangements may be used if desired.

In a typical arrangement, the production tubing head 12 has a circular spool shape and includes a lower attachment flange 26 as well as an upper attachment flange 28. As will be appreciated, the lower attachment flange 26 and the upper attachment flange 28 each typically includes a multiplicity of bolt holes arranged circumferentially about the perimeter outboard from the axial bore 16. Connection bolts may be run through the bolt holes to permit attachment of other structures at either end of the production tubing head 12.

In accordance with the present invention, a sealing adapter 30 may be operatively connected across the upper attachment flange 28. As will be described further hereinafter, the sealing adapter 30 acts to provide a secondary sealing barrier for the production tubing head 12 when fracturing operations are complete. The sealing adapter 30 also provides protection for the tubing hanger 14.

Referring now jointly to FIGS. 1-3, in the illustrated exemplary embodiment, the sealing adapter 30 includes an annular body 32 which may be mounted in fixed relation across the upper attachment flange 28 of the production tubing hanger 12 by use of attachment bolts 34 (FIG. 2) extending downwardly for engagement with complementary bolt holes arranged circumferentially about the upper attachment flange 28. By way of example only, and not limitation, the annular body 32 may be formed from cast steel or other suitable metal, although non-metallic materials may also be used if desired. As shown, the annular body 32 may be secured in place by nuts 36 which engage the attachment bolts 34. In this regard, it will be understood that in actual practice attachment bolts 34 typically will be disposed circumferentially about the annular body 32 for connection using complementary nuts. By way of example only, and not limitation, one such exemplary pattern is illustrated in FIG. 3. However, it is likewise contemplated that a larger or smaller number of bolt positions may be used if desired. As illustrated, attachment bolts 34 may also extend outwardly from an upper surface of the annular body 32 for attachment to additional structures (not shown).

As illustrated, the annular body 32 includes an axial channel 40 for disposition in substantial alignment with the axial bore 16 of the production tubing head 12. Thus, the neck of the tubing hanger 14 may project upwardly into the axial channel 40. As best seen through joint reference to FIGS. 2 and 3, the annular body 32 also includes an arrangement of radial channels for mounting extendable and retractable pins. In this regard, a first radial locator channel 42 and a second radial locator channel 44 are disposed in opposing relation to one another on either side of the axial channel 40. The first radial locator channel 42 is adapted to hold a first locator pin 46 which may be extended and retracted radially relative to the axial channel 40. The second radial locator channel 44 is adapted to hold a second locator pin 48 which also may be extended and retracted radially relative to the axial channel 40. As shown in FIG. 2, the second locator pin 48 is longer than the first locator pin 46.

In the illustrated exemplary arrangement, the annular body 32 further includes a first set of radial locking pin channels 50 which are adapted to hold a first set of locking pins 52 which may be extended and retracted radially relative to the axial channel 40. In the illustrated exemplary arrangement, the annular body 32 further includes a second set of radial locking pin channels 56 which are adapted to hold a second set of locking pins 58 which may be extended and retracted radially relative to the axial channel 40. In the illustrated exemplary configuration the first set of locking pins 52 are longer and thinner than the second set of locking pins 58.

FIG. 3 illustrates one exemplary pattern for placement of the locator pins 46, 48 and the first set of locking pins 52 around the circumference of the annular body 32. In this exemplary arrangement, the individual locking pins 52 are arranged at positions between the locations of the attachment bolts 34. The second set of locking pins 58 may be arranged in substantially the same pattern as the first set of locking pins 52. However, other positional arrangements may be used if desired such that the first set of locking pins 52 may be offset from the second set of locking pins 58 if desired.

As shown, the sealing adapter 30 includes a dummy hanger designated generally as 60 adapted for sliding insertion into the axial channel 40. In the illustrated exemplary construction the dummy hanger 60 includes an annular sleeve insert 62 and an axial plug 64 of substantially solid construction which is matedly inserted into the interior bore of the annular sleeve insert 62. Both the annular sleeve insert 62 and the axial plug 64 may be formed from a steel alloy or other suitable material as may be desired.

As best seen in FIG. 2, in the exemplary embodiment the lower edge of the annular sleeve insert includes a first positioning notch 66 which is configured to accept the distal end of the first locator pin 46 when the first locator pin 46 is in an inserted condition. Thus, by advancing the first locator pin 46 into the axial channel 40 and then inserting the annular sleeve insert 62, both the height and rotational orientation of the annular sleeve insert 62 are established. In this regard, it will be understood that the width of the first positioning notch 66 preferably closely matches the distal end of the first locator pin 46 to prevent substantial rotational movement following initial placement. Likewise, the outer diameter of the annular sleeve insert 62 preferably matches closely with the inner diameter of the axial channel 40 to prevent the annular sleeve insert from tilting within the axial channel 40.

As shown, the annular sleeve insert 62 includes a reduced diameter neck 68 which extends circumferentially about the annular sleeve insert 62. As best seen in FIG. 2, the reduced diameter neck 68 is positioned to engage distal ends of the upper locking pins 58 when the annular sleeve insert has engaged the first locator pin 46 and the upper locking pins have been advanced into the axial channel 40. Thus, by advancing the upper locking pins 58, the annular sleeve insert may be locked in place against axial withdrawal.

As shown, the annular sleeve insert 62 further includes a number of pin receiving channels 65 which are oriented to be in substantial alignment with the first set of radial locking pin channels 50. Thus, distal ends of the lower locking pins 52 may project through the pin receiving channels 65 to engage the exterior of the axial plug 64. Thus, by advancing the lower locking pins 52, the axial plug 64 may be locked in place against axial withdrawal.

The annular sleeve insert 62 and the axial plug 64 cooperatively form a double barrier seal relative to the tubing hanger 14 and the operatively connected production tubing head 12. In this regard, in the illustrated exemplary construction the annular sleeve insert 62 includes a pair of circumferential grooves 70 which are adapted to hold a first set of o-rings 72 or other compressible seals. As will be appreciated, the o-rings 72 provide a tight seal between the annular sleeve insert 62 and the inner wall of the annular body 32. In this regard, the o-rings 72 are spaced apart from one another along the height of the annular sleeve insert 62 to provide a double seal relationship. Thus, even if one seal fails, the overall sealing relation nonetheless remains intact.

As noted previously, the axial plug 64 is configured to be slidingly inserted into the interior bore of the annular sleeve insert 62. Alternatively, rather than use the axial plug 64, the user can adapt a type H back pressure valve that is threadingly inserted into the sleeve 62. The fullbore back pressure valve axial plug 64 allows the use of a production tree that matches the bore of the tubing used in the completion. For instance, where a type H back pressure valve is used in the lower hanger and a 2″ full bore axial plug 64 is used in the upper hanger, a 2 1/16″ bore production tree can be installed on the well. In this example, when a type H back pressure valve is used in both the upper and lower hanger, a 2″ back pressure valve is used in the lower hanger and a 2½″ back pressure value is used in the upper hanger. This installation would then require the use of a larger 2 9/16″ bore production tree. As best seen in FIG. 2, in the exemplary embodiment the lower edge of the axial plug 64 includes a second positioning notch 76 which is configured to accept the distal end of the second locator pin 48 when the second locator pin 48 is in an inserted condition. When the annular sleeve insert 62 is oriented such that the first locator pin engages the first positioning notch 66, the second locator pin 48 will be aligned with a radial positioning channel 78 in the wall of the annular sleeve insert 62. Thus, once the annular sleeve insert 62 is in place, the second locator pin 48 may be advanced through the radial positioning channel 78 to project into the inner bore of the annular sleeve insert. Accordingly, by first advancing the second locator pin 48 to the position illustrated in FIG. 2, and then inserting the axial plug 64, both the height and orientation of the axial plug 64 are established within the inner bore of the annular sleeve insert 62. As will be appreciated, the width of the second positioning notch 76 preferably closely matches the distal end of the second locator pin 48 to prevent substantial rotational movement following initial placement. In addition, the outer diameter of the axial plug 64 preferably matches closely with the inner diameter of the annular sleeve insert 62 to prevent the axial plug 64 from tilting within the annular sleeve insert 62.

In the illustrated exemplary construction, the axial plug 64 includes a pair of circumferential grooves which are adapted to hold a second set of o-rings 80 or other compressible seals. As will be appreciated, the second set of o-rings 80 provides a tight seal between the axial plug 64 and the inner wall of the annular sleeve insert 62. In this regard, the o-rings 80 are spaced apart from one another along the height of the axial plug 64 to provide a double seal relationship. Thus, even if one seal fails, the overall sealing relation between the axial plug 64 and the annular sleeve insert remains intact.

As shown, in the exemplary configuration the first set of o-rings 72 is oriented in staggered relation to the second set of o-rings 80 such that each o-ring is at a different height within the sealing adapter 30. Such an arrangement may aid in the efficacy of the overall sealing relation.

In at least one exemplary embodiment, one or more testing ports may extend through the annular body 32. These testing ports are arranged at different heights along the sealing adapter 30 to permit monitoring of performance at different locations. By way of example only, in the illustrated exemplary embodiment a first testing port 82 is positioned at a height between the tubing hanger 14 and the bottom of the dummy hanger 60. As will be appreciated, the sealing performance of the tubing hanger 14 can be monitored at the first testing port 82. A second testing port 84 is positioned at a height between the upper and lower members of the first set of o-rings 72. As will be appreciated, by monitoring the pressure at the second testing port 84, the performance of the seals formed by the lower o-rings 72 can be evaluated. A third testing port 86 is positioned at a height above the seals and the reduced diameter neck 68 on the annular sleeve insert 62. Thus, by monitoring the pressure at the third testing port 86, the overall sealing performance of the sealing adapter may be evaluated. Moreover, in the event that a proper sealing relation is not being achieved, the positions of the various testing ports permit a user to diagnose the location where the sealing function has failed.

In practice, the annular body 32 may be installed across the production tubing head 12 before fracturing operations take place. After installation of the tubing hanger 14, the system may be pressure tested using the first testing port 82 to confirm proper sealing. The first locator pin 46 may then be extended such that the distal end projects into the axial channel 40. With the first locator pin 46 in the extended position, the annular sleeve insert 62 is then inserted in substantially coaxial relation with the annular body 32 and with the first positioning notch 66 fitting about the distal end of the first locator pin 46. The height and rotational relation of the annular body 32 is thus established. The second set of locking pins 58 may then be advanced to engage the reduced diameter neck 68 to lock the annular sleeve insert 62 in place. A pressure test may then be performed through the second testing port 84.

Once the annular sleeve insert 62 is properly positioned, the second locator pin 48 may be advanced through the radial positioning channel 78 in the annular sleeve insert 62 such that the distal end of the second locator pin 48 extends into the bore of the annular sleeve insert 62. With the second locator pin 48 in the extended position, the solid axial plug 64 may be inserted in substantially coaxial relation with the annular body 32 and annular sleeve insert 62 and with the second positioning notch 76 fitting about the distal end of the second locator pin 48. The height and rotational relation of the axial plug 64 is thus established. The first set of locking pins 52 may then be advanced to lock the axial plug 64 in place. A pressure test may then be performed through the third testing port 86 to confirm the overall sealing function.

In use, the sealing adapter 30 provides an effective second barrier across the production tubing head 12 once fracturing operations are complete and the fracturing equipment has been removed. In particular, the sealing adapter 30 acts to protect the neck of the tubing hanger 14 or other primary sealing device while nonetheless providing access by removal of the solid axial plug 64.

As seen in an alternative embodiment in FIG. 4, the tubing head 12 and sealing adaptor 30 may be forged from a single piece rather than connecting the sealing adaptor 30 to the tubing head In this embodiment, it will be readily understood that the attachment bolts 34 and nuts 36 are no longer required. Other than being formed from a single piece rather than separate tubing head and sealing adaptor, the operation of this embodiment is the same as that of the embodiment shown in FIGS. 1 through 3.

Of course, variations and modifications of the foregoing are within the scope of the present invention. Thus, it is to be understood that the invention disclosed and defined herein extends to all alternative combinations of two or more of the individual features mentioned or evident from the text and/or drawings. All of these different combinations constitute various alternative aspects of the invention. The embodiment described herein explain the best modes for practicing the invention and will enable others skilled in the art to utilize the invention. The claims are to be construed to include alternative embodiments and equivalents to the extent permitted by the prior art.

The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.

Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.

Various features of the invention are set forth in the following claims. 

1. An adapter for disposition in sealing relation to a tubing head operatively connected to a hydrocarbon well, the adapter comprising: an annular body adapted to be secured in fixed relation to the tubing head, the annular body including an axial channel, a first set of radial locking pin channels extending radially away from the axial channel and at least a second set of radial locking pin channels extending radially away from the axial channel, the second set of radial locking pin channels being axially spaced from the first set of radial locking pin channels; a dummy hanger adapted to be matedly inserted into the axial channel, the dummy hanger including an annular sleeve insert having a central bore and a removable axial plug disposed within the central bore of the annular sleeve insert, the annular sleeve insert including a plurality of pin receiving channels extending radially through the annular sleeve insert for aligned relation with the first set of radial locking pin channels; a first set of extendable and retractable locking pins disposed within the first set of radial locking pin channels, the first set of extendable and retractable locking pins including distal ends adapted to project through the pin receiving channels in the annular sleeve insert to engage the axial plug; a second set of extendable and retractable locking pins disposed within the second set of radial locking pin channels, the second set of extendable and retractable locking pins including distal ends adapted to engage the annular sleeve insert; a first compressible seal disposed circumferentially about the annular sleeve insert; at least a second compressible seal disposed circumferentially about the annular sleeve insert in axially spaced relation from the first compressible seal; at least a third compressible seal disposed circumferentially about the axial plug; and at least a fourth compressible seal disposed circumferentially about the axial plug in axially spaced relation from the third compressible seal.
 2. The adapter as recited in claim 1, further including a testing port in fluid communication with the axial channel at a position below the first set of radial locking pin channels.
 3. The adapter as recited in claim 1, further including a testing port in fluid communication with the axial channel at a position between the first set of radial locking pin channels and the second set of radial locking pin channels.
 4. The adapter as recited in claim 1, further including a testing port in fluid communication with the axial channel at a position above the first set of radial locking pin channels and the second set of radial locking pin channels.
 5. The adapter as recited in claim 1, further including a first testing port in fluid communication with the axial channel at a position below the first set of radial locking pin channels, a second testing port at a position between the first set of radial locking pin channels and the second set of radial locking pin channels and a third testing port at a position above the first set of radial locking pin channels and the second set of radial locking pin channels.
 6. The adapter as recited in claim 1, wherein the annular sleeve insert includes a reduced diameter neck adapted to engage distal ends of the second set of extendable and retractable locking pins.
 7. The adapter as recited in claim 1, wherein the third compressible seal is normally disposed at an elevation between the first compressible seal and the second compressible seal and the fourth compressible seal is normally disposed at an elevation below the first compressible seal and the second compressible seal.
 8. The adapter as recited in claim 1, wherein the annular sleeve insert includes a first positioning notch disposed at a lower edge and the axial plug includes a second positioning notch disposed at a lower edge, and wherein a first extendable and retractable locator pin is disposed within a first radial locator channel, the first extendable and retractable locator pin including a distal end adapted to project into the axial channel to engage the first positioning notch at the annular sleeve insert, and wherein a second extendable and retractable locator pin is disposed within a second radial locator channel, the second extendable and retractable locator pin including a distal end adapted to project across the annular sleeve insert to engage the second positioning notch at the axial plug.
 9. The adapter as recited in claim 8, wherein the first extendable and retractable locator pin is disposed at substantially the same elevation as the second extendable and retractable locator pin.
 10. An adapter for disposition in sealing relation to a tubing head operatively connected to a hydrocarbon well, the adapter comprising: an annular body adapted to be secured in fixed relation to the tubing head, the annular body including an axial channel, a first set of radial locking pin channels extending radially away from the axial channel and at least a second set of radial locking pin channels extending radially away from the axial channel, the second set of radial locking pin channels being axially spaced apart from the first set of radial locking pin channels, a first radial locator channel extending radially away from the axial channel, and at least a second radial locator channel extending radially away from the axial channel, the first radial locator channel and the second radial locator channel each being disposed at axial positions below the first set of radial locking pin channels and the second set of radial locking pin channels; a dummy hanger adapted to be matedly inserted into the axial channel in substantially coaxial relation to the annular body, the dummy hanger including an annular sleeve insert having a central bore and a removable axial plug disposed within the central bore of the annular sleeve insert in substantially coaxial relation with the annular sleeve insert, the annular sleeve insert including a first positioning notch disposed at a lower edge and a plurality of pin receiving channels extending radially through the annular sleeve insert for aligned relation with the first set of radial locking pin channels, and a radial positioning channel extending radially through the annular sleeve insert to the central bore for aligned relation with the second radial locator channel, the axial plug including a second positioning notch disposed at a lower edge; a first extendable and retractable locator pin disposed within the first radial locator channel, the first extendable and retractable locator pin including a distal end adapted to project into the axial channel to engage the first positioning notch at the annular sleeve insert; a second extendable and retractable locator pin disposed within the second radial locator channel, the second extendable and retractable locator pin including a distal end adapted to project across the annular sleeve insert to engage the second positioning notch at the axial plug, a first set of extendable and retractable locking pins disposed within the first set of radial locking pin channels, the first set of extendable and retractable locking pins including distal ends adapted to project through the pin receiving channels in the annular sleeve insert to engage the axial plug; a second set of extendable and retractable locking pins disposed within the second set of radial locking pin channels, the second set of extendable and retractable locking pins including distal ends adapted to engage the annular sleeve insert; a first compressible seal disposed circumferentially about the annular sleeve insert; at least a second compressible seal disposed circumferentially about the annular sleeve insert in axially spaced relation from the first compressible seal; at least a third compressible seal disposed circumferentially about the axial plug; and at least a fourth compressible seal disposed circumferentially about the axial plug in axially spaced relation from the third compressible seal, wherein each of the first, second, third and fourth compressible seals are disposed axially between the first set of extendable and retractable locking pins and the second set of extendable and retractable locking pins.
 11. The adapter as recited in claim 10, further including a testing port in fluid communication with the axial channel at a position below the first set of radial locking pin channels.
 12. The adapter as recited in claim 10, further including a testing port in fluid communication with the axial channel at a position between the first set of radial locking pin channels and the second set of radial locking pin channels.
 13. The adapter as recited in claim 10, further including a testing port in fluid communication with the axial channel at a position above the first set of radial locking pin channels and the second set of radial locking pin channels.
 14. The adapter as recited in claim 10, further including a first testing port in fluid communication with the axial channel at a position below the first set of radial locking pin channels, a second testing port at a position between the first set of radial locking pin channels and the second set of radial locking pin channels and a third testing port at a position above the first set of radial locking pin channels and the second set of radial locking pin channels.
 15. The adapter as recited in claim 10, wherein the annular sleeve insert includes a reduced diameter neck adapted to engage distal ends of the second set of extendable and retractable locking pins.
 16. The adapter as recited in claim 10, wherein the third compressible seal is normally disposed at an elevation between the first compressible seal and the second compressible seal and the fourth compressible seal is normally disposed at an elevation below the first compressible seal and the second compressible seal.
 17. The adapter as recited in claim 10, wherein the first extendable and retractable locator pin is disposed at substantially the same elevation as the second extendable and retractable locator pin.
 18. A method of applying a secondary seal across a tubing head operatively connected to a hydrocarbon well, the method comprising the steps of: providing an annular body including an axial channel, a first set of radial locking pin channels extending radially away from the axial channel and at least a second set of radial locking pin channels extending radially away from the axial channel, the second set of radial locking pin channels being axially spaced from the first set of radial locking pin channels; securing the annular body in fixed relation to the tubing head; providing an annular sleeve insert having a central bore and including a plurality of pin receiving channels extending radially through the annular sleeve insert for aligned relation with the first set of radial locking pin channels; providing a first compressible seal disposed circumferentially about the annular sleeve insert and at least a second compressible seal disposed circumferentially about the annular sleeve insert in axially spaced relation from the first compressible seal; inserting the annular sleeve insert with the first compressible seal and at least second compressible seal into the axial channel of the annular body; providing an axial plug having an outer diameter substantially matching the inner diameter of the annular sleeve insert; inserting the axial plug into the central bore of the annular sleeve insert; extending a set of locking pins disposed within the second set of radial locking pin channels such that distal ends of the locking pins engage the annular sleeve insert; and extending another set of locking pins disposed within the first set of radial locking pin channels such that distal ends of the locking pins project through the pin receiving channels in the annular sleeve insert and engage the axial plug.
 19. The method as recited in claim 18, wherein the annular sleeve insert includes a first positioning notch disposed at a lower edge and the axial plug includes a second positioning notch disposed at a lower edge, and wherein a first extendable and retractable locator pin is extended into the axial channel to engage the first positioning notch at the annular sleeve insert such that the rotational position and height of the annular sleeve insert is fixed, and wherein a second extendable and retractable locator pin is extended across the annular sleeve insert to engage the second positioning notch at the axial plug such that the rotational position and height of the axial plug is fixed.
 20. A tubing head including a sealing portion, the sealing portion comprising: an annular body formed in the upper portion of the tubing head, the annular body including an axial channel, a first set of radial locking pin channels extending radially away from the axial channel and at least a second set of radial locking pin channels extending radially away from the axial channel, the second set of radial locking pin channels being axially spaced from the first set of radial locking pin channels; a dummy hanger adapted to be matedly inserted into the axial channel, the dummy hanger including an annular sleeve insert having a central bore and a removable axial plug disposed within the central bore of the annular sleeve insert, the annular sleeve insert including a plurality of pin receiving channels extending radially through the annular sleeve insert for aligned relation with the first set of radial locking pin channels; a first set of extendable and retractable locking pins disposed within the first set of radial locking pin channels, the first set of extendable and retractable locking pins including distal ends adapted to project through the pin receiving channels in the annular sleeve insert to engage the axial plug; a second set of extendable and retractable locking pins disposed within the second set of radial locking pin channels, the second set of extendable and retractable locking pins including distal ends adapted to engage the annular sleeve insert; a first compressible seal disposed circumferentially about the annular sleeve insert; at least a second compressible seal disposed circumferentially about the annular sleeve insert in axially spaced relation from the first compressible seal; at least a third compressible seal disposed circumferentially about the axial plug; and at least a fourth compressible seal disposed circumferentially about the axial plug in axially spaced relation from the third compressible seal. 